J. C. van 't Spijker, P. Dorenbos, C. W. E. van Eijk, K. Krämer and H. U. Güdel
Scintillation and luminescence properties of Ce³⁺ doped K₂LaCl₅
J. Lumin. 85, 1-10 (1999)                 

Abstract: Scintillation and luminescence properties of K₂LaCl₅ : Ce³⁺ with Ce³⁺ concentrations between 0.001% and 10% are presented. Under optical excitation the characteristic double-peaked Ce³⁺ luminescence is observed between 330 and 380 nm. Under X-ray excitation also self-trapped exciton (STE) luminescence ranging from 250 to > 500 nm is also observed. At low Ce³⁺ concentration the STE luminescence is dominant. The largest light yield is observed for K₂LaCl₅ : 10% Ce³⁺ where 97% of the emission intensity stems from Ce³⁺ luminescence. For this sample the light output is 50000 ph/MeV under continuous X-ray excitation and 31300 ph/MeV under g excitation. Two models are proposed to explain the energy transfer from the host lattice to the Ce ions. At low Ce³⁺ concentration energy transfer by STE diffusion is proposed, whereas at high Ce³⁺ concentration energy transfer by bimolecular recombination is held dominant.